The Spanish invention patent with application number 9602019, of the same applicant, describes a horizontal formwork made up, as is conventional, of a lower substrate of beams supported on struts and an upper substrate of beams perpendicular to the foregoing, complemented finally by upper panels that constitute the formwork surface.
On the basis of these characteristics, in the said invention patent, in order to achieve high flexion strength in the beams, the latter are made of metallic plate and with a special design that gives rise to a reduction of weight in comparison to conventional beams.
Specifically, the said invention patent claims the fact that the beams of the lower substrate are made from a thin steel plate and form in their upper part the classic channelling for holding the also classic wooden strip, while in their lower part they have connection cylinders, both in their end areas and at the intermediate points where they are to be supported on struts. In the latter case they are to be coupled by means of tongue and groove inside the said struts, and at the ends they are to be coupled to intermediate joining parts which, with a general "U" shape, are able to receive in their interior the ends of two adjoining beams, having for this purpose lateral is holes for coupling the connection cylinders of the said beams, while in the middle they have another connection cylinder, projecting downwards, for coupling the corresponding strut.
For their part, the beams of the upper substrate are made up of a structure relatively similar to that of the beams of the lower substrate, but without connection cylinders. The beams of the upper substrate have a great profusion of orifices in their side walls, which give rise to a substantial lightening of material; some of these orifices, rectangular in shape, are obtained by stamping out and pressing, defining wings that project perpendicularly towards the inside of the beam, which make the structure of the same considerably more rigid.
In spite of the fact that the horizontal formwork obtained in accordance with what is described and claimed in the said Spanish invention patent No. 9602019, effectively fulfills the objectives for which it was conceived, nevertheless when the beams are subjected to very great stresses they may undergo warping, which may cause them to open.